Yep, that's my co2 reactor. Nothing inside of it except a piece of hard air line tubing, the kind from a UGF lift tube. I drilled a hole in the top bushing, put the air line tubing in to about half way down, and siliconed it in place. Water flow from my sunsun exits the canister, goes into the top of the reactor, flows down while co2 bubbles flow up, making for the best saturation in the water. I should've made the reactor a little longer, as I am still getting some micro bubbles in my tank. But that's ok, I can then see the co2 getting pushed around the tank. The brass piece you see is a check valve.